The present patent application is related to fiber optic networks, and, in particular, to switches for WDM and DWDM network systems.
In WDM (Wavelength Division Multiplexing) fiberoptic networks, optical signals are sent at predetermined wavelengths over optical fibers. Each predetermined wavelength forms a communication channel in the network and the wavelength (or frequency) of the optical signal is used to control the destination of the signal through the network. An advanced version of WDM networks is the DWDM (Dense Wavelength Division Multiplexing) network in which the number of wavelength channel is increased by reducing the channel wavelength separation. In DWDM networks, the communication channels are separated by 100 GHz, as set by the ITU (International Telecommunications Union) and the fiberoptic industry is already assuming an unofficial channel separation of 50 GHz for advanced DWDM networks.
In passing, it should be noted that the term, DWDM, is used to refer to both WDM and DWDM networks and other fiberoptic networks which rely upon wavelength to define communication channels, unless indicated otherwise.
In such fiberoptic networks, switches arc used to select paths for optical signals through the optical fibers forming the networks, i.e., to direct optical signals from one optical fiber to another and from one wavelength channel to another. Hence switches tend to be large, complex and expensive systems; installation, repair and reconfiguration (if possible) are time-consuming and costly. It is desirable that a switch be scalable so as to meet the requirements of a DWDM network on an xe2x80x9cas-neededxe2x80x9d basis so as to avoid unwanted costs, that the switch be easily repaired and reconfigured to avoid costly xe2x80x9cdown timexe2x80x9d for network in operation.
The present invention is directed toward such a fiberoptic switch.
The present invention provides for a network switch for a DWDM network having a plurality of optical fibers, each optical fiber carrying M wavelength channels. The network switch controllably switches signals on N input optical fibers to N output optical fibers of said DWDM network and has a control unit, a plurality of demultiplexers, a plurality of tunable channel units, a switch fabric and a plurality of combiners. Each demultiplexer is connected to one of the N input optical fibers and separates signals by the wavelength channels into a plurality of demultiplexer output terminals. Each tunable channel unit is connected to one of the demultiplexer output terminals associated with one of the wavelength channels and is capable of switching signals in a first wavelength channel into a second wavelength channel responsive to signals from the control unit. The switch fabric has a plurality of input terminals and output terminals, each input terminal is connected to an output terminal of one of the tunable channel units. The switch fabric has Mxc3x97N2 switch points and is arranged so that a signal on any one of its input terminals can be sent to any one of its output terminals responsive to signals from the control unit. Each combiner has a plurality of input terminals connected to the output terminals of the switch fabric and an output terminal connected to one of said N output optical fibers.